// Copyright (c) 2024 PaddlePaddle Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "paddle/phi/core/kernel_registry.h"
#include "paddle/phi/kernels/funcs/eigen/common.h"

namespace phi {

template <typename T, typename Context>
void AddPositionEncodingGradKernel(const Context& dev_ctx,
                                   const DenseTensor& x_in,
                                   const DenseTensor& out_grad,
                                   float alpha,
                                   float beta,
                                   DenseTensor* x_grad) {
  auto* dOut = &out_grad;
  auto dout = phi::EigenVector<T>::Flatten(*dOut);

  auto* dX = x_grad;
  dev_ctx.template Alloc<T>(dX);
  auto dx = phi::EigenVector<T>::Flatten(*dX);

  auto* place = dev_ctx.eigen_device();
  dx.device(*place) = dout * static_cast<T>(alpha);
}
}  // namespace phi

PD_REGISTER_KERNEL(add_position_encoding_grad,
                   CPU,
                   ALL_LAYOUT,
                   phi::AddPositionEncodingGradKernel,
                   float,
                   double) {}
